This invention relates to a composition for use in manufacturing ingots from which parts can be made having heat, thermal shock, corrosion and wear resistance. The method and composition herein is particularly used in manufacturing plungers for use in the glass container manufacturing industry.
Because of thermal shock, wear, and scratches due to particulate contamination in molten glass, there is an increased interest in development of strong, heat resistant, thermal shock, corrosion, and wear resistant material for use in manufacturing plungers as substitutes for cobalt, nickel cast alloys and stainless steel parts presently used in the glass industry. It has been discovered that nickel aluminide, NiAl, composites have good applicability for this purpose because of their high melting temperatures, hardness, and corrosion resistance.
Nickel aluminide has many different stoichiometric compounds. These compounds have significantly different properties. Ni.sub.3 Al with small amounts of boron, or hafnium, or zirconium is disclosed in U.S. Pat. No. 4,612,165. The material was investigated for the U.S. Department of Energy as a substitute for stainless steel. It can be cast into ingots, cold rolled and fabricated into many shapes.
The nickel aluminide used in this disclosure, that is, NiAl, has a much higher melting temperature and is harder than Ni.sub.3 Al but it cannot be cast and still retain its stoichiometric compound. When it is cast the nickel aluminide undergoes a phase separation into nickel and aluminum. This effect can be recognized when studying the phase diagrams in Vol. 8, pp. 262, Eighth Edition of "The American Society For Metals, Metal Handbook". When phase separation takes place the alloy's melting temperature drops significantly and it loses some of its corrosion resistances.
Although several alloy compounds of nickel aluminide exist, NiAl has the favorable characteristic of a high melting temperature, that is, 1640.degree. C. It has been discovered that a composite formed of NiAl and titanium diboride has unexpected levels of hardness and decreased wear rates. The composite formed of NiAl and TiB.sub.2 is characterized by its high temperature properties, high hardness and its lack of depressing the melting point of NiAl.
The NiAl composites of this disclosure are excellent engineering materials and it is expected that they will find many other uses in fabrication of components for turbines, pumps, wear seals, wear plates, foundry tools and other equipment or tools that are exposed to severe wear, thermal shock, and/or high temperatures. The addition of certain platelets, ceramic whiskers or fibers serve to increase the high temperature strength.
For information relating to other compositions having charactistics of hardness of high temperatures and thermal shock and corrosion resistance, see the following U.S. Pat. Nos. 2,915,801; 3,248,215; 3,311,522; 3,413,392; 4,325,734; 4,382,053; 4,612,165; 4,711,761; 4,722,828; 4,731,221, 4,747,990; 4,801,415 and 4,961,903.